1. Field of the Invention
This invention relates to a process for preparing an alkanolammonium salt or ammonium salt of surface active agents and more particularly, to a novel process for preparing an alkanolammonium salt or ammonium salt of an amino acid surface active agent or an acrylated amino acid surface active agent.
2. Description of the Prior Art
In view of a recent trend toward the safety and low stimulativeness, imidazoline amphoteric surface active agents and amino acid surface active agents have been widely used in shampoo bases and various detergents because of their low stimulativeness. Especially, imidazoline amphoteric surface active agents are ease in the manner of preparation and are inexpensive, so that they have been widely used and extensively studied.
In general, imidazoline amphoteric surface active agents are prepared by reacting alkylimidazolines with sodium monochloroacetate. The imidazoline amphoteric surface active agents obtained by the above process have been found by recent studies to be amidoamine derivatives which are products obtained by ring opening of imidazolines, but little imidazoline skelton which has been long considered as contained has not been present in the agents. For instance, the agents have the following structure (I) ##STR1## in which R represents an alkyl group.
Accordingly, this type of imidazoline amphoteric surface active agent may be prepared by reaction between an amidoazmine and sodium monochloroacetate.
When the alkali metal salt of the surface active agent is converted to an alkanolammonium salt or an ammonium salt, it exhibits good miscibility with water-soluble polymers and various additives because of the low ion strength. In addition, because of the low Krafft point, such an agent has good stability at low temperatures. For known processes of preparing alkanolammonium salts or ammonium salts of the imidazoline amphoteric surface active agents, the alkali metal salts of the imidazoline amphoteric surface active agents (e.g. sodium salts) are treated with a mineral acid to give an acid form, followed by neutralization with an alkanolamine or ammonia.
However, the above process is disadvantageous in that when the acid form is produced by treatment with a mineral acid, sodium chloride is formed in large amounts to cause gelation or mineral acid salt of the amine is produced, making it difficult to efficiently produce an alkanolammonium salt or an ammonium salt. For instance, when an imidazoline amphoteric surface active agent of the formula (I) was treated with hydrochloric acid as a mineral acid and subsequently neutralized with triethanolamine, an intended product of (I)-a with high purity could be obtained but only a mixture of (I)-a - (I)-c and (I) was obtained as shown in the following reaction formula ##STR2## in which R has the same meaning as defined before.
These phenomena take place commonly in all the cases including amino acid surface active agents and acylated amino acid surface active agents. As a result, the resultant product inevitably contain large amounts of impurities such as salts (e.g. NaCl). Thus, these alkanolammonium salts or ammonium salts of these surface active agents cannot exhibit inherent characteristic properties such as good miscibility with various additives and low temperature stability.